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Appendix B
Register-Level Programming
DAQCard-DIO-24 User Manual
B-4
©
National Instruments Corporation
Interrupt Control Registers
The DAQCard-DIO-24 has two interrupt control registers. One of these
registers has individual enable bits for the two interrupt lines from the
82C55A. The other register has a master interrupt enable bit. The bit
maps and signal definitions follow.
Interrupt Control Register 1
Bit
Name
Description
7–2
0
Reserved—These bits must be set to zero
for compatibility with future versions of
this card. However, older software that
sets these bits to 1 will still work with the
DAQCard-DIO-24.
1
IRQ1
Interrupt Selection 1—If this bit and the
INTEN bit in Interrupt Control
Table B-2.
Port C Set/Reset Control Words
Number
Bit Set Control Word
Bit Reset Control Word
Bit Set or Reset in Port C
0
0XXX0001
0XXX0000
XXXXXXXn
1
0XXX0011
0XXX0010
XXXXXXnX
2
0XXX0101
0XXX0100
XXXXXnXX
3
0XXX0111
0XXX0110
XXXXnXXX
4
0XXX1001
0XXX1000
XXXnXXXX
5
0XXX1011
0XXX1010
XXnXXXXX
6
0XXX1101
0XXX1100
XnXXXXXX
7
0XXX1111
0XXX1110
nXXXXXXX
D7
D6
D5
D4
D3
D2
D1
D0
0
0
0
0
0
0
IRQ1
IRQ0